1. Field of the Invention
Rotation control detectors are frequently used in numerous industries for monitoring movement, slipping, conveyor belt breaks, belt breaks, etc. They unite, in the same device, conventional functions of detecting the presence of a target close to, or in contact with, the detector by means of a sensor element and functions of processing by counting the information received by the detector during a given time for comparison with, for example, a predetermined frequency of engagement of the device so as to deliver as an output a binary signal resulting from this comparison. An economical device is thus obtained, well suited to dealing with simple problems of under-speed and over-speed.
2. Description of the Related Art
The document EP 1130403 describes a rotation-monitoring detector, in front of which there passes a target whose frequency of passage is to be monitored with respect to a normal passage frequency. This detector comprises operator communication means constituted by a push button and an electroluminescent communication diode LED on the detector. The push button acts to place the detector in a working mode or in a learning mode. The learning mode permits the microcontroller of the detector to measure a normal passage frequency and permits selecting a range of detector functioning around this normal frequency. In the learning mode, the communication LED associated with the push button acts, for example, to guide the operator in the adjustment of the desired range of detector functioning. Furthermore, such a detector also generally comprises a display LED which is the image of the state of the output.
However, during the mounting of a rotation-monitoring detector, it is hardly practical to adjust the distance of the target in static mode so as to situate it in the range of the detector. For this, it would be quite effective to give the assembly operator, during the initial adjustment phase, information indicating to him whether or not the target is placed at a satisfactory distance within the range of the detector. There exist certain rotation-monitoring detectors which have for this purpose, as well as an LED to display an image of the frequency of passage of the target, another specific display LED whose state is a function of the distance between the target and the detector. However, this solution is expensive, because it requires a supplementary display component which is only used in the initial adjustment phase and which can furthermore result in excessive electric consumption in a small size device, particularly in a two-wire supply version.